/*
 * Copyright 2009 Cedric Priscal
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.goodocom.gocsdk;

import java.io.File;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.util.Log;

public class SerialPort {

    private static final String TAG = "SerialPort";

    /*
     * Do not remove or rename the field mFd: it is used by native method
     * close();
     */
    /**
     * 文件描述符类的实例用作与基础机器有关的某种结构的不透明句柄，该结构表示开放文件、开放套接字或者字节的另一个源或接收者。
     * 文件描述符的主要实际用途是创建一个包含该结构的 FileInputStream 或 FileOutputStream。
     */
    private FileDescriptor mFd;
    private FileInputStream mFileInputStream;
    private FileOutputStream mFileOutputStream;

    // 构造方法
    public SerialPort(File device, int baudrate, int flags) throws SecurityException, IOException {

        /*
         * // Check access permission if (!device.canRead() ||
         * !device.canWrite()) { try { //Missing read/write permission, trying
         * to chmod the file Process su; su =
         * Runtime.getRuntime().exec("/system/bin/su"); String cmd =
         * "chmod 666 " + device.getAbsolutePath() + "\n" + "exit\n";
         * su.getOutputStream().write(cmd.getBytes()); if ((su.waitFor() != 0)
         * || !device.canRead() || !device.canWrite()) { throw new
         * SecurityException(); } } catch (Exception e) { e.printStackTrace();
         * throw new SecurityException(); } }
         */
        mFd = open(device.getAbsolutePath(), baudrate, flags);
        if (mFd == null) {
            Log.e(TAG, "native open returns null");
            throw new IOException();
        }
        // 通过使用文件描述符 fdObj 创建一个 FileInputStream，该文件描述符表示到文件系统中某个实际文件的现有连接。
        mFileInputStream = new FileInputStream(mFd);
        mFileOutputStream = new FileOutputStream(mFd);
    }

    // Getters and setters
    public InputStream getInputStream() {
        return mFileInputStream;
    }

    public OutputStream getOutputStream() {
        return mFileOutputStream;
    }

    // JNI
    private native static FileDescriptor open(String path, int baudrate, int flags);

    public native void close();

    static {
        System.loadLibrary("serial_port");
    }
}
